1. Field of the Invention
The invention relates to the use of particular azole compounds for enhancing the resistance of plants to abiotic stress factors. The present invention further provides a spray solution which comprises particular azole compounds and can be used for enhancing the resistance of plants to abiotic stress factors. The present invention finally also relates to a method for treatment of plants or plant parts for enhancing resistance to abiotic stress factors.
2. Description of Related Art
A fundamental distinction among possible causes of damage to plants is between biotic and abiotic causes. Most of the biotic causes of damage to plants are known pathogens, which can be controlled by chemical crop protection measures and by resistance breeding. In contrast, abiotic stress is the effect of individual or combined environmental factors (in particular frost, cold, heat and drought) on the metabolism of the plant, which constitutes an unusual stress for the organism. In this context, tolerance to abiotic stress means that plants are capable of enduring the stress situation with substantial retention of performance or with less damage than is observed with corresponding, more stress-sensitive controls.
The effect of moderate stresses over prolonged periods of time or short-term extreme stress may lead to irreversible damage, up to and including the death of the plants. Abiotic stress factors are thus responsible to a considerable degree for harvest losses, or lead to average harvests that are often distinctly below the maximum possible yield (Bray et al.: “Responses to Abiotic Stresses”, in: Buchanan, Gruissem, Jones (eds.) “Biochemistry and Molecular Biology of Plants”, pages 1158 to 1203, American Society of Plant Physiologists, 2000).
It is known that chemical substances may increase the tolerance of plants to abiotic stress. Such effects, which are frequently also associated with increased yields, are also observed inter alia when particular fungicides are used and have been demonstrated for the group of the strobilurins (Bartlett et al., 2002, Pest Manag Sci 60: 309).
For some azole compounds too, a stress resistance-promoting effect has already been demonstrated. However, this has to date been restricted to azoles of a particular structure type (for example methylazoles); to azoles in combination with abscisic acid (ABA); to azoles causing a significant depression of growth in the treated plants; to applications of the azoles in the treatment of seed or seedlings and to the reduction of damage caused by artificial ozone treatment (see, for example, WO 2007/008580 A; Imperial Chemical Industries PLC, 1985, Research Disclosure 259: 578-582; CA 211 98 06; JP 2003/325063 A; Wu and von Tiedemann, 2002, Environmental Pollution 116: 37-47).
In addition, effects of growth regulators on the stress tolerance of crop plants have been described, including paclobutrazole, a methylazole used as a growth regulator (Morrison and Andrews, 1992, J Plant Growth Regul 11: 113-117; Imperial Chemical Industries PLC, 1985, Research Disclosure 259: 578-582).
The effect of abscisic acid (ABA) as a phytohormone has been described in a large number of physiological processes. For example, ABA acts as a “stress hormone”, the formation of which is induced inter alia by drought stress and, inter alia, mediates inhibition of stomatary transpiration (closure of the stomata) (Schopfer, Brennicke: “Pflanzenphysiologie” [Plant Physiology], 5th edition, Springer, 1999). This makes the plant more tolerant to drought stress.
It has been shown in numerous examples that exogenous application of abscisic acid can reduce the sensitivity of plants to stress, or increase stress tolerance (Jones and Mansfield, 1970, J. Exp. Botany 21: 714-719; Bonham-Smith et al., 1988, Physiologia Plantarum 73: 27-30). Furthermore, it was also shown that ABA-analogous structures are capable of triggering ABA-like plant reactions (Churchill et al., 1998, Plant Growth Regul 25: 35-45; Huang et al., 2007, Plant J 50: 414-428). The stress tolerance-enhancing action of ABA analogs in combination with growth inhibitors has likewise already been described (DE 38 215 20 A).
The fungicidal action of azoles such as tebuconazole and prothioconazole is known and is based on the inhibition of sterol C14-demethylase, a central enzyme in sterol biosynthesis (Kuck & Vors: “Sterol Biosynthesis Inhibitors”, in: Krämer & Schirmer (eds.) “Modern Crop Protection Compounds”, Vol. 2, pages 605 to 650, Wiley-VCH, 2007).
In addition to sterol C14-demethylase, however, other enzymes of the same type (known as P450 monooxygenases) are also inhibited by representatives of these substance classes. For example, many of these molecules also lead, as a result of inhibition of ent-kaurene oxidase after application, to significant stunting of the plants, since the biosynthesis of gibberellic acid is thus inhibited, a plant hormone involved, inter alia, in the regulation of growth processes (Buchenauer: “DMI-fungicides—side effects on the plant and problems of resistance, in: Lyr (ed.) “Modern Selective Fungicides”, 2nd ed., p. 259-290, Gustav Fischer Verlag, 1995).
Some representatives of these substance classes have additionally also been described as inhibitors of abscisic acid catabolism (specifically of ABA hydroxylation by ABA 8′-hydroxylase) (Kitahata et al., 2005, Bioorg. Med. Chem. 13: 4491-4498; Saito et al., 2006, Biosci. Biotechnol. Biochem. 70: 1731-1739; Zhang et al., 2007, Journal of Plant Physiology 164: 709-717). The substances described therein, diniconazole and uniconazole, lead, however, to an undesired degree of stunting in some crop plants, for example oilseed rape. The use of these and some other azoles in combination with abscisic acid to increase plant resistance to abiotic stress is described in WO2007/008580 A.
JP 2003-325063 discloses the use of some azoles for treatment of seedlings, which are planted in the soil by means of a machine. The findings described therein are not applicable to a treatment of plants or plant parts to increase resistance to abiotic stress, since the substances act on different plant structures, organs and tissue in seeds and seedlings (for example, cotyledons are physiologically and morphologically different leaves) and are also absorbed via different routes (seed kernel or seedling tissue as opposed to wax layer and leaf tissue of a further-developed plant).